Method of producing photographic dyestuff images



Patented June 11, 19 35 PATENT orrica METHOD OF PRODUCING PHOTOGRAPHIC DYES'IUFF IMAGES Bela Gaspar, Berlin, Germany No Drawing. Application February 14, 1933, lsg'gal No. 656,764. In Germany February 15,

6 Claims.

This invention relates to a method of producing photographic dyestufi images.

In my prior application Serial No. 572232 I have described methods by which diffusely colored dyestufi' images containing metallic silver are subsequently destroyed at the points of the silver deposit.

It has been found, that this destruction of the dyestuif may also be performed at an earlier stage 10 in the production of the silver image, viz., during the developing process or immediately thereafter. It has been proposed to perform development and simultaneous destruction of the dyestuff image by means of a sodium hydrosulphite solution. It is known, however, that a silver halide layer cannot be developed in proper fashion with sodium hydrosulphite alone. This method possesses the disadvantage that silver halide layers treated with a sodium hydrosulphite solution acquire very easily a haze, and therefore supply merely imperfect color images. Beyond this a part of the silver halide image is converted into sulphite of silver and the majority of dyestufis are very readily diffusely decolored by sodium hydrosulphite in a concentration in which the same is effective.

Now it has been found that very good results may be obtained and the dyestufi destroyed in proper fashion during the development itself, the surprising fact being that this may be accomplished with extremely different means. Generally speaking it is possible to produce good dyestufi images if, for example, a developing substance or other weak reducing substance, which in itself will not destroy the dyestufi, is allowed to act onan acid agent or is combined with other weak reducing means. An agent of this nature is, for example, sodium bisulfite. For example the acid amidol developer in the known composition, viz.,

Grammes Amidol Sodium bisulfite 1 crystallized sodium sulfite 8 Water 200 amidol developer, which has acid added thereto during the development; or that development is commenced with a neutral amidol developing solution, and the treatment then continued in a second developer, to which a certain amount of acid has been added. Different acids and also the most different types of developers, such as pyrogallol, metol, glycin, etc., and also different combinations of these may be employed. For example a layer is diffusely colored with chloramine light red 7 BL or with diamine gold yellow CP. Good results may also be obtained in accordance with the invention with the assistance of solutions of powerful reducing substances, assuming that these are employed in low concentration, so that the same do not diffusely decolor the dyestufi, and suitable auxiliary substances added thereto. These additions consist of weak reducing substances, which considerably accelerate the action, fogpreventing agents, such as bromide of potassium, imidazole substances, etc., and possibly acids. In the following example sodium bisulfite. constitutes the weak reducing agent and at the' same time acid substance.

- Grammes Sodium hydrosulfite 0.5 Bromide of potassium 1 Sodium bisulfite 3 Water Other combinations are also possible, for example neutral or slightly acidified developer with silver dissolving complex-forming substances, such as thiourea derivatives, guanidine sulfate, cystin, etc., or reducing agents such as titanium trichloride, sodium hydrosulfite, etc. In addition there may also be mentioned the combination with rongalite, sulfides and other substances capable of reduction. Thesedyestuff-destroying developing baths may in accordance with the invention be employed in all cases in which the dyestufi is not destroyed until afterwards at the point of the silver image, in conjunction with diffusely colored silver halide layers, in which a plurality of layers are poured one upon the other, and in connection with materials sensitized on both sides, or in conjunction with equivalent arrangements in which a plurality of differently colored sensitized emulsions are mixed together; or also in respect of kinematograph films containing images and sound records, etc. In the same manner local reducing development is also possible if there are present in the layer not the dyestufis themselves but the preliminary stages thereof, i. e., dyestuff-forming substances, as described,

veloping the exposed silver halide and reducing the colored dyestufi at the same points that development is taking place with a bath containing a weak reducing agent and an acid reacting agent.

2. A method of producing photographic dyestufl images in an emulsion containing silver halide and a dye capable of being decolorized by reduction, which consists in simultaneously developing the exposed silver halide and reducing the colored dyestuff at the same points that development is taking place with a bath containing developing substances and strong reducing substances in weak concentration in mixture with an acid reacting agent and an additional accelerating agent.

3. A method of producing photographic dyestuif images in an emulsion containing silver halide and a dye capable of being decolorized by reduction, which consists in simultaneously developing the exposed silver halide and reducing the colored dyestuif at the same points that development is takingmlace with a bath containing sodium hydro-sulfite, bromide 01 potassium and sodium bisulflte.

4. A method of producing photographic dyestufi images on combined picture and sound films having an emulsion containing silver halide and a dye capable of being decolorized by reduction which consists in simultaneously developing the exposed silver halide and reducing the colored dyestufi at the same points that development is,

acid reacting agent.

6. A method of producing photographic dyestuff images in an emulsion containing silver halide and a dye capable of being decolorized by reduction, which consists in simultaneously developing the exposed silver halide and reducing the colored dyestuff at the same points that development is taking place, the development being commenced in a normal developer and continued in a developer which contains in addition to the developing substance a weak reducing agent and an acid reacting agent.

. BELA GASPAR. 

